The present invention is directed to a fuel comprised of sewage sludge and a solid particulate fuel.
In an effort to reduce oil consumption due to volatile oil prices and questionable future sources of supply, industry has begun to convert from oil-fired boilers to boilers which are fired by alternative fuels such as particulate coal, coal-water and coal-oil mixtures. Admixtures of coal with suitable liquids such as water and oil are attractive as alternative fuels since such pumpable admixtures are relatively easily adapted for use with oil-fired boilers. This is contrast to the effort which is required to convert an oil-fired boiler to a coal-fired boiler. Exemplary disclosures of coal-water fuels are provided by U.S. Pat. No. 3,660,054 (issued to Rieve), U.S. Pat. No. 3,762,887 (issued to Clancey et al), U.S. Pat. No. 4,104,035 (issued to Cole et al), and U.S. Pat. Nos. 4,282,006; 4,416,666; 4,468,232; 4,477,259; 4,477,260; and 4,479,806 (each issued to Funk).
It is also known that alternative fuels may be comprised of a coal-sewage admixture which is processed prior to burning for various reasons such as to decrease the moisture content thereof, etc. See, for example, U.S. Pat. No. 3,166,032 (issued to Klesper); U.S. Pat. No. 4,135,888 (issued to Waltrip); U.S. Pat. No. 4,159,684 (issued to Kirkup) and British Pat. No. 949,000 (issued to Passavant et al). However, the production of such coal-sewage fuels requires significant processing and results in a substantially non-pumpable fuel which possesses the above-noted disadvantages of fuels comprised substantially of particulate coal.
It is also known to provide aqueous mixtures of sewage sludge which include a particulate fuel such as coal as exemplified by U.S. Pat. No. 4,405,332 (issued to Rodriguez et al) and Japanese patent publication No. 55-94996.
While such technology is generally acceptable, a need exists to modify the properties of the sewage sludge to enhance the physical characteristics of the ultimate admixture (e.g., the pumpability and stability of the admixture).
It would also be an advantage to provide an alternative fuel comprised of a solid fuel such as particulate coal and a relatively readily available waste material, such as sewage, which provides the advantages of pumpable coal-containing fuels while avoiding the disadvantages of substantially solid particulate fuels.
It would also be an advantage to provide an improved method for the disposal of sewage sludge which avoids the need for conventionally employed methods whereby the sewage sludge is treated and eventually discarded in landfills, etc. Such methods are costly, time-consuming and prevent valuable land from being used for more beneficial purposes.